The present invention relates, in general, to methods and systems for separating isotopes from nuclear reactors, and in particular to a method employed in reactors and used for medical isotope production.
Beginning in 1945, nuclear reactors were used to produce medical isotopes employing various techniques. U.S. Pat. No. 4,487,738 teaches a method for producing a Cu isotope for diagnostic and experimental medical applications. The Cu isotope is produced by proton spallation combined with subsequent chemical separation and purification.
U.S. Pat. No. 3,914,373 discloses a method for separating isotopes by contacting a feed solution containing the isotopes with a cyclic polyether. This method has been applied to clinical, biological and medical research.
U.S. Pat. No. 4,158,700 discloses a method of producing radioactive Technetium-99m using a solution containing Molybdenum-99 and Technetium-99m in conjunction with a chromatographic column and eluting it with a neutral solvent system comprising an organic solvent for producing Technetium-99m as a dry, particulate residue.
U.S. Pat. No. 3,799,883 discloses dissolving uranium material in aqueous inorganic acid then precipitating Mo-99 using alpha-benzoinoxime.
An article entitled "Study of the Separation of Molybdenum-99 and Recycling of Uranium to Water Boiler Reactor" by W. L. Cheng, et al., Appl. Radiot. Isot., Vol. 40, No. 4, pp. 315-324, 1989, teaches a process which includes the separation of Molybdenum-99 from uranium sulfate fuel solution with an .alpha.-benzoin oxime precipitation and purification by chelating ion exchanger, alumina, and calcium phosphate hydroxide as adsorbents.
Although the isotope Molybdenum-99 (Mo-99) is an isotope commonly used in the medical field, only one method exists for the production of medical isotopes such as Mo-99 that is approved by the United States Food and Drug Administration. This method comprises extracting the fission product, Mo-99, from a Uranium-235 target which has been irradiated in a neutron flux provided by a large nuclear reactor. Because these nuclear reactors are used for other purposes besides producing medical isotopes, the reactor power is high, usually 20,000 to 200,000 kilowatts. When producing medical isotopes this power output by the nuclear reactor is extremely wasteful.